Slipform with longitudinally movable form sections

ABSTRACT

This invention relates to slipforms for forming a smooth concrete surface along a prepared soil surface such as within a tunnel or an open trench. The slipform includes a plurality of separate elongated form sections mounted side by side or end to end. Powered cylinders are connected between the form sections. The cylinders are cyclically operated to successively move each form section in a repeated sequence along a longitudinal path against the combined static friction of at least two other sections which remain stationary during such movement.

Hanson 14 1 Apr. 15, 1975 SLIPFORM WITH LONGITUDINALLY MOVABLE FORM SECTIONS 3,377,669 4/l968 Burgess 425/59 [76] Inventor: Raymond A. Hanson, c/o R. A. Primary Baldwin Hanson Co, p BOX 7400 Asszstant Examiner-John McQuade Spokane, Wash 99207 Attorney, Agent, or FzrmWells, St. John & Roberts [22] Filed: May 4, 1973 57 ABSTRACT [21] Appl. No.: 357,453 1 This invention relates to slipforms for forming a smooth concrete surface along a prepared soil surface [52] 1.1.8.5: 425/5]9:, such as Within a tunnel or an open trench The slip o m ncludes a o ep elongated form [58] 0 earc 2 sections mounted side by side or end to end. Powered 3 0 cylinders are connected between the form sections. The cylinders are cyclically operated to successively [56] References C'ted move each form section in a repeated sequence along UNITED STATES PATENTS a longitudinal path against the combined static friction 2,520,199 8/1950 Butcher 425/59 of at least two other sections which remain stationary 3,032,852 5/1962 Hanson 425/59 during such movement. 3,049,783 8/1962 Hanson..... 425/219 3,206,824 10/1965 Cerutti 425/59 12 Claims, 18 Drawing Figures I s F $6 7 (N/ 0 '.'-:':"\'l :1. .1 Ujf-"LH 3' '7' 20 m, 3e 3e 1 2+ 7 29m a a a; 3/ 22 r 2 r i" a -1" S '3- o '1 1 1 7 If FATENTEE 1 5i9-75 3,877. 855

sum 1 o 5 FIG 5 79; FIG 3 PATENTEB I 9 5 3, 877. 855

sum 3 95 g PATENTEEAPR 1 Sims 3. 7 855 sum u 95 5 FIG 16 SLIPFORM WITH LONGITUDINALLY MOVABLE FORM SECTIONS BACKGROUND OF THE INVENTION The apparatus disclosed herein relates in general to slipforms for surfacing materials. It is applicable to many slipform configurations, particularly to such forms utilized to form a lining or pipeline along a previously formed excavation such as a tunnel or open ditch.

Difficulty has been experienced in moving such slipforms along ditches and especially through tunnels. Prior slipforms in tunnels have been moved along by pressure of concrete or other surfacing materials pumped into the form or have been pulled along by a cable from a stationary or moving towing unit. Because of inconsistencies occuring in both the concrete mixture and the working environment, the pressure method for moving such forms has been proven to be relatively inefficient. The cable method requires use of additional equipment separate from the slipform and which would normally interfere with tunnel boring operations.

The apparatus disclosed below includes an integral means for moving the slipform within a tunnel or ditch without utilizing pressure of the surfacing material flow or a separate towing unit. The slipform is instead mobilized by a series of hydraulic cylinders connecting lon gitudinally movable form sections to one another. The cylinders are operated to move each form section successively against the combined static friction of the remaining form sections.

While specifically helpful in forming inner circumferential bores, the basic structure disclosed herein is also applicable to the design of slipforms for lining open canals, trenches or even flat concrete roadways or walks.

The form also might include hinged wall sections which allow longitudinal turning of the form as it moves along the placed concrete.

SUMMARY OF THE INVENTION The slipform invention comprises a plurality of partial form sections movable longitudinally relative to one another while smoothing concrete or other surfacing material placed upon a prepared soil surface. Supply means for the surfacing material places it upon the soil surface and the forms slide along at a chosen spacing from the soil surface. Power is applied individually between adjacent form sections to move each form section incrementally relative to the other form sections, which serve as reactors to permit propulsion along the surfacing material while it remains in a plastic state.

One object is to provide a simple self-moving form for surfacing material as it is placed along a longitudinal path. Movement is accomplished by power units which can be located within the confines of the slipform itself.

Another object is to provide a self-moving slipform that provides open equipment access at both ends for support framework and auxiliary machinery.

Other objects will be evident from the following detailed discussion of a practical embodiment.

DESCRIPTION OF THE DRAWINGS FIG. 1 is an isometric pictorial view of a first embodiment of the slipform;

FIG. 2 is an enlarged elevational sectional view taken along line 22 in FIG. 1;

FIG. 3 is a detailed elevational view ofa typical longitudinal hinge joining two longitudinally adjacent slipform side panels;

FIG. 4 is a detailed view of a typical walking cylinder connected between two laterally adjacent slipform panels;

FIG. 5 is a side view of one end of the connection illustrated in FIG. 4;

FIG. 6 is a longitudinal cross-section of the slipform within a tunnel and in operation;

FIG. 7 is an end view of the slipform in operation;

FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 6;

FIGS. 9-11 are diagrammatic views illustrating the operation of the invention;

FIG. 12 is an isometric pictorial view of a second embodiment of the slipform;

FIG. 13 is a cross-sectional view of the slipform in operation taken along line l313 in FIG. 12;

FIG. 14 is an elevational sectional view of the slipform in operation taken along line 14-14 in FIG. 12;

FIG. 15 is a perspective view of a third embodiment of the slipform;

FIG. 16 is a reduced cross-sectional view of the slipform taken along line 1616 in FIG. 15;

FIG. 17 is a top view of the slipform in FIG. 15; and

FIG. 18 is a longitudinal section view taken along line 18-18 in FIG. 17.

DESCRIPTION OF A PREFERRED EMBODIMENT The disclosed apparatus is concerned with the forming of concrete or other surfacing material being placed along a longitudinal path, such as the length of a roadway, sidewalk, canal, trench, pipeline or tunnel. The slipform surfaces the material immediately after its placement on a prepared soil surface. The specific slipform is self-moving, utilizing the static friction of a portion of the form against the freshly-placed material as a reaction member.

The illustrated slipform of FIGS. 1-11 is adapted to form a continuous concrete bore either in a tunnel, open ditch or similar sub-soil excavation utilizing a full circular inner form. When forming pipeline or concrete lining in a tunnel, the tunnel walls are used as outside forms. In an open ditch, the bottom of the ditch serves partially as an outside form with the upper part of the pipeline being formed by the moving machine.

The machine, is designed to move under its own power along a ditch or tunnel in a forward direction of travel as indicated by the arrow in FIG. 6. Respective elements of the slipform described below will be referred to with respect to the forward direction of travel noted above.

It should be noted that the circular cross-section of the form is shown in the drawings only by way of example and that other enclosed curvilinear or polygonal cross-sectional shapes are conceivable.

Referring now to the drawings in greater detail and especially to FIG. I, the slipform is shown basically comprising a longitudinal tubular form 10 with a front end 11 and a back end 18. The tubular form is constructed of a plurality of arcuate wall sections connected by hinges 38 end to end to form three identical longitudinally slidable form sections 10a, 10b and 10c.

Hinges 38 and the longitudinal spaces between adjacent wall sections are provided to allow for slight amounts of curvature in the path of the form. A resilient filler 19 of material such as rubber may be placed between the ends of the wall sections as shown in FIG. 3 to prevent leakage of wet concrete into the interior of the form while also allowing relative angular movement between adjacent wall sections.

A longitudinal triangular truss-type framework 17 mounts a circular consolidator ring support 13 at the front end 11 and a ring mount 15 on back end 18. Rings 13 and 15 slidably mount sections 10a, 10b and 10c in a circular cross-section along longitudinal slide joints formed. by their abutting longitudinal side edges.

Also fixed to frame 17 is an angularly spaced front set of ground engaging wheels 21 and a back set ofwheels 23 which may be elevated to ride along the finished concrete surface (FIG. 6). The front wheel frame includes an adjusting cylinder 22 which may be selectively activated to adjust the elevation of the form as it moves along.

Concrete is supplied by conventional pump means or other conveyors (not illustrated) to'an oscillating consolidator ring section 14 through a length of pipe 24. A water pipe 20 also leads to consolidator ring 14 to facilitate adjustment of the ratio mixture at ring 14 as needed.

Consolidator ring 14 includes an integral inner circumferential wall section 25 (FIG. 6), a vertical closed front wall section 26 and an outer circumferential wall 27 which together define a rearwardly open passageway for dispersal of concrete therefrom. The inner wall section 25 has an inwardly projecting circumferential way 28 which slidably fits within a complementary annular recess guide 30 in the stationary ring support 13. This slidable relationship provides for oscillation of consolidator 14 by means of a pair of hydraulic cylinders 31.

Cylinders 31 are mounted on opposite lateral sides of the slipform with each having a base end mounted to stationary ring support 13 and a piston end extending upwardly to a forwardly projecting bracket 32 on the front wall 26 of consolidator 14. Oscillational movement of consolidator 14 is effected as one cylinder is extended while the other is retracted. Such oscillational movement of the consolidator serves to unify or consolidate the concrete mixture about the form as it moves along.

Additional information concerning further details of the consolidator generally described above may be obtained by reference to my US. Pat. No. 3,049,783 issued on Aug. 21, 1962.

The means utilized for propelling the form along a tunnel or ditch may best be understood with reference to FIGS. 2, 4-6 and 8-11. The means illustrated comprises a system of three double acting hydraulic cylinders joining adjacent form sections 10a, 10b and 100; and a like number of retarder cylinders 34, 35, 36 connecting each form section to frame 17.

Sections 10a, 10b and 100 are selectively moved by double acting cylinders 40, one of which is shown in FIG. 4. Three such cylinders 40 are utilized to progressively walk the form along as demonstrated in FIGS. 9-11. Cylinders 40 are mounted parallel to the longitudinal axis of the form at positions adjacent the slide joints between form sections 10a, 10b and 100. Each cylinder 40 includes a front piston shaft 41 and a coaxial, rearwardly extending piston shaft 42. Front shafts 41 are connected to forward mounting brackets 43 of the form sections with the rear shafts 42 connected to rearward mounting bracket 44 of the adjacent form I sections on the other sides of the same slide joints. The 1 cylinder 40 shown in FIG. 4 connects the front bracket 43 of form section 10a to the rear bracket 44 of an adjacent section b. Each form section includes a forward bracket 43 on one longitudinal side edge and a rear bracket 44 on the other edge so when the form sections are fitted together, the front brackets 43 are aligned with complementary rear brackets 44..

Since the form sections are identical and in contact I with a common material (concrete), the friction between each section and the wet or plastic concrete presents equal amounts of resistance to longitudinal movement. In operation, the resistance of two sections are combined by locking the two sections toone another. The combined resistance of the two locked sections provides a reaction force during forward movement of the remaining section. Controlled alternating operation of cylinders 40 in a repeating sequence is utilized to move each section in turn to walk the form longitudinally along the ditch or tunnel. The operational cycle or sequence may be controlled by a suitable rotary valve or other sequencing device, shown generally at 29.

The single operational cycle of cylinders 40 as shown by FIGS. 9-11 is repeated continuously to move the form along a ditch or tunnel. Before explanation of this 3 cycle, however, it should be understood that the form sections are shown in a flat configuration and that the single cylinder 40 is joining form sections and 100 is shown as two separate cylinders. This has been done solely for the purpose of diagrammatically illustrating the operational sequence as clearly as possible. FIG. 8 illustrates the true relationship with a single cylinder 40 joining form sections 10a and 10c as reaction elements.

The next section 10a is then moved forwardly a distance equal to that moved by section 10b as the cylinder 40 between section 10b and 100 is locked and the cylinders on either side of section 10a are activated as indicated by the arrows to push section 10a from one side and to pull it from the other side. A similar process is then followed (FIG. 11) as the cylinder 40 between sections 10a and 10b is locked and the cylinders on either side of section, 100 are activated, as shown by the arrows, to move that section 100 forwardly into transverse alignment with the other two sections by combined pushing and pulling efforts.

The above operation is repeated continuously to progressively move the form along a tunnel or ditch as the concrete is deposited through the consolidator l4. The speed of movement of the form along a tunnel or ditch may be controlled by selectively altering time intervals 1 between each operational step described above. The speed is regulated so the concrete adjacent the rear end of the form has reached a self-supporting consistency before the form moves on. This speed is necessarily variable to accommodate changes in drying time due to concrete mixture, dampness in the tunnel or ditch, or other unforseen environmental changes, occurring as the form moves along.

The retarder cylinders 34, 35 36 serve to progressively move the frame and elements attached thereto.

along in response to individual movements of the form sections. Cylinders 34, 35, 36 may best be seen in FIGS. 2 and 6. As shown in FIG. 2 the cylinders are mounted between form section 10a and the frame. Cylinders 35, 36 are mounted between the frame 17 and i form sections b and 10c respectively. The cylinders 34, 35, 36 are connected in a closed fluid circuit so that movement of one cylinder affects equal movement of the other two. With such a circuit, one third of the movement of each form section is transferred to the frame 17. Thus, in one operational cycle, with each form section moving a set distance of, for example 6 inches. The total distance moved by the frame would be the sum of three 2 inch intervals or 6 inches.

FIGS. 12, l3 and 14 illustrate the general application of this invention to the paving of an upwardly open surface area such as a longitudinal trench, canal, or a flat roadway. In these applications, using three or more sections of the form arranged transversely across the'path of the structure, it is necessary to provide a physical connection between the outermost form sections at each side of the device and the remaining form section to provide an imbalanced reaction system analagous to that described above in a completely enclosed slipform.

The second form of the apparatus is used in the paving of a canal trench having a bottom wall 41 and upwardly inclined side walls 42. The desired configuration of the mass of concrete 43 is shown in FIG. 13. The concrete is placed immediately forward of the slipform by means of a hopper 44 having a forward wall 45 that extends vertically to edges which are adjacent to the walls 41 and 42. Hopper 44 is carried by a longitudinal frame 46, whose weight is borne by the slipform and by a front wheel assembly 47.

The slipform is fashioned in three sections. The center section extends across the bottom of the trench and partially up both sides. It is designated in the drawings by the numeral 50. The side sections 51, 52 are mirror images of one another. They have lower longitudinal edges which extend parallel to the bottom wall 41 and slidably engage the upper edges at each side of central form sections 50.

Relative movement between the form sections 50, 51, and 52 is provided by double-acting cylinder assemblies 53, which are operatively joined between the central section 50 and each side section 51, 52 and also between longitudinal frame extensions 54, 55, which are fixed along the upper edges of the side sections 51, 52 respectively. Thus, while the forms themselves do not extend around a complete circumferential path, the extensions 54, 55 complete the structural arrangement analagous to that described above with respect to FIGS. l-ll.

Movement of form sections 50, 51 and 52 is accomplished sequentially with the cylinder assembly 53 at one side of a section exerting a pulling force as the two sections connected to them serve as stationary reaction members. The two reacting form sections are locked relative to each other by the cylinder connecting them 55 during the time of movement of the one form section.

The frame 46 is independent of each form section 50, 51 and 52 being slidably engaged with each section to maintain the desired cross-sectional configuration of the form sections. Again, it is movably connected to each of the form sections by means of a series of retarder cylinders 56. The cylinders 56 are connected to one another within a closed fluid circuit so that movement of one cylinder affects equal movement of the other two. One third of the movement of each form section is therefore transferred to frame 46, causing frame 56 to move the full distance traversed by any single form section only after all three form sections have been so moved.

it is believed that the operation of this form of the invention is understandable from the drawings and its clear relationship to the form of the invention described in greater detail with respect to FIGS. l-ll.

The third form of the invention (FIGS, 15-18) utilizes longitudinally aligned form sections rather than the transversely positioned form sections of the preceding embodiments.

Each form section 60, 61 and 62 is essentially identical, having integral reinforcing frames and outwardly facing smooth plates complementary to the desired concrete surface configuration. However, the first section further includes concrete placement chutes 63 at each side, joined to one another at 64 across the bottom of the unit. Hoppers 65 receive incoming concrete and direct it into chutes 63, where it is placed on the soil surfaces for smoothing by the slipform.

The form sections are progressively moved by a forward set of cylinders 66 and a rear set of cylinders 67, both being double ended and double acting. When cylinders 66 are activated to push form section 60 forwardly, the form sections 61, 62 act as reaction members. Cylinders 67 are next used to push form section 61 forwardly, while cylinders 66 pull form section 61 forwardly, using form sections 60, 62 as reaction members. Finally, the cylinders 67 pull forwardly on form section 62, using form sections 60, 61 as reaction members. In this manner, incremental movement is achieved in a repeated operational cycle. Turning is achieved by moving the cylinders at one side a distance less than the movement of the cylinders at the remaining side.

It may become obvious that various changes and modifications may be made with respect to the above description and the appended drawings. For example, more than three longitudinal form sections could be utilized, along with an equal number of cylinders 40 to provide for more friction reaction by the locked sections and less drag on the moving section. The invention disclosed is intended, therefore, to be defined only by the following claims.

I claim:

1. A slipform for smoothing the exposed surfacing material placed upon a prepared soil surface during longitudinal movement of the slipform along the surface, comprising:

a plurality of partial form sections arranged adjacent to one another having outer surface areas complementary to the desired surface configuration, adjacent form sections each being longitudinally slidable on said surfacing material relative to the remaining form sections;

supply means for placement of surfacing material in a plastic state along the prepared soil surface forward of the form sections;

and individually operable power means connecting the form sections to one another for selectively imparting longitudinal sliding motion to one form section along said surfacing material relative to the other form sections and relative to the placed surfacing material;

said individually operable power means comprising independent power assemblies located along the sides of the form sections at inner surfaces thereof, each power assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.

2. A slipform as set out in claim 1 wherein said individually operable power means comprise independent longitudinal fluid cylinder assemblies located along the form sections, each cylinder assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.

3. A slipform as set out in claim 2 further comprising:

control means operably connected to each of the cylinder assemblies for sequentially actuating each cylinder in a repetitive cycle to move each form section longitudinally along the excavation. 4. A slipform for use within a longitudinal subsoil excavation for forming a longitudinal finished surface along a plastic mass placed about the slipform within the excavation along excavation surfaces, comprising:

a plurality of partial form sections having outer surfaces arranged adjacent to one another and together presenting the desired cross sectional configuration of the finished surface about their outer surfaces, with adjacent form sections having longitudinal side edges thereof in sliding engagement with one another to permit longitudinal movement of an individual form section on said finished surface relative to the remaining form sections;

supply means for placement of surfacing material in a plastic state within the excavation in contact with the outer surfaces of the form sections;

and individually operable power means operatively connecting each form section to the remaining form sections for selectively imparting longitudinal motion to the form section relative to the remaining form sections;

said individually operable power means comprising independent power assemblies located along the sides of the form sections at inner surfaces thereof, each power assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.

5. A slipform as set out in claim 4 wherein said individually operable power means comprise independent longitudinal fluid cylinder assemblies located along the sides of the form sections at inner surfaces thereof, each cylinder assembly being operatively connected between two of said form sections so as to impart rela tive sliding movement between them when actuated.

6. A slipform as set out in claim 5 further comprising:

control means operably connected to each of the cylinder assemblies for sequentially actuating each cylinder in an identical manner in a repetitive cycle to slide each form section longitudinally along the excavation.

7. A slipform as set out in claim 4 wherein the slipform includes longitudinal open ends;

and an elongated rigid support frame extending.

within the slipform and operatively connected to the form sections as a support therefore, including means in contact with the excavation surfaces for locating the form sections relative to the excavation surfaces.

8. A slipform for use within a longitudinal subsoil excavation for forming a longitudinal interior bore within a plastic mass placed about the slipform within the excavation, comprising:

three or more longitudinally elongated partial form sections, each having an identical transversely ar-.

cuate convex outer surface area of constant configuration along its length;

supply means for placing surfacing material about the circumference of the assembled form sections while filling the space between the walls of the ex- 7 cavation and form sections;

and individually operable power means connecting each form section to the respective form sections adjacent to it on each side for imparting longitudinal movement to a single form section on said plastic mass relative to at least two other form sections;

said individually operable power means being comprised of independent power assemblies, each.

power assembly being connected between two of said form sections so as to depart relative sliding movement between themwhen actuated. 9. A slipform as set outin claim 8 wherein said individually operable power means is comprised ofindependent longitudinal fluid cylinder assemblies, each. 1 cylinder assembly being connected between two of said form sections so as to impart relative sliding movement between them when actuated.

10. A slipform as set out in claim 9 further compris ing:

control means operably connected to each of the cylinder assemblies for sequentially actuating each.

cylinder in a repetitive cycle to slide each form section longitudinally along the excavation. 11. A slipform as set out in claim 8 wherein the partial form sections are identical to one another, each outer surface being transversely arcuate and elongated longitudinally and presenting a portion of a full circular circumferential surface in combination with the outer surface areas of the remaining partial form sections 

1. A slipform for smoothing the exposed surfacing material placed upon a prepared soil surface during longitudinal movement of the slipform along the surface, comprising: a plurality of partial form sections arranged adjacent to one another having outer surface areas complementary to the desired surface configuration, adjacent form sections each being longitudinally slidable on said surfacing material relative to the remaining form sections; supply means for placement of surfacing material in a plastic state along the prepared soil surface forward of the form sections; and individually operable power means connecting the form sections to one another for selectively imparting longitudinal sliding motion to one form section along said surfacing material relative to the other form sections and relative to the placed surfacing material; said individually operable power means comprising independent power assemblies located along the sides of the form sections at inner surfaces thereof, each power assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.
 2. A slipform as set out in claim 1 wherein said individually operable power means comprise independent longitudinal fluid cylinder assemblies located along the form sections, each cylinder assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.
 3. A slipform as set out in claim 2 further comprising: control means operably connected to each of the cylinder assemblies for sequentially actuating each cylinder in a repetitive cycle to move each form section longitudinally along the excavation.
 4. A slipform for use within a longitudinal subsoil excavation for forming a longitudinal finished surface along a plastic mass placed about the slipform within the excavation along excavation surfaces, comprising: a plurality of partial form sections having outer surfaces arranged adjacent to one another and together presenting the desired cross-sectional configuration of the finished surface about their outer surfaces, with adjacent form sections having longitudinal side edges thereof in sliding engagement with one another to permit longitudinal movement of an individual form section on said finished surface relative to the remaining form sections; supply means for placement of surfacing material in a plastic state within the excavation in contact with the outer surfaces of the form sections; and individually operable power means operatively connecting each form section to the remaining form sections for selectively imparting longitudinal motion to the form section relative to the remaining form sections; said individually operable power means comprising independent power assemblies located along the sides of the form sections at inner surfaces thereof, each power assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.
 5. A slipform as set out in claim 4 wherein said individually operable power means comprise independent longitudinal fluid cylinder assemblies located along the sides of the form sections at inner surfaces thereof, each cylinder assembly being operatively connected between two of said form sections so as to impart relative sliding movement between them when actuated.
 6. A slipform as set out in claim 5 further comprising: control means operably connected to each of the cylinder assemblies for sequentially actuating each cylinder in an identical manner in a repetitive cycle to slide each form section longitudinally along the excavation.
 7. A slipforM as set out in claim 4 wherein the slipform includes longitudinal open ends; and an elongated rigid support frame extending within the slipform and operatively connected to the form sections as a support therefore, including means in contact with the excavation surfaces for locating the form sections relative to the excavation surfaces.
 8. A slipform for use within a longitudinal subsoil excavation for forming a longitudinal interior bore within a plastic mass placed about the slipform within the excavation, comprising: three or more longitudinally elongated partial form sections, each having an identical transversely arcuate convex outer surface area of constant configuration along its length; supply means for placing surfacing material about the circumference of the assembled form sections while filling the space between the walls of the excavation and form sections; and individually operable power means connecting each form section to the respective form sections adjacent to it on each side for imparting longitudinal movement to a single form section on said plastic mass relative to at least two other form sections; said individually operable power means being comprised of independent power assemblies, each power assembly being connected between two of said form sections so as to depart relative sliding movement between them when actuated.
 9. A slipform as set out in claim 8 wherein said individually operable power means is comprised of independent longitudinal fluid cylinder assemblies, each cylinder assembly being connected between two of said form sections so as to impart relative sliding movement between them when actuated.
 10. A slipform as set out in claim 9 further comprising: control means operably connected to each of the cylinder assemblies for sequentially actuating each cylinder in a repetitive cycle to slide each form section longitudinally along the excavation.
 11. A slipform as set out in claim 8 wherein the partial form sections are identical to one another, each outer surface being transversely arcuate and elongated longitudinally and presenting a portion of a full circular circumferential surface in combination with the outer surface areas of the remaining partial form sections whereby said slipform may be utilized to form an interior bore within said plastic mass.
 12. A slipform as set out in claim 11 wherein the partial form sections complement one another when assembled to present a transverse closed inner form having a circumferential outer surface for forming the bore, with longitudinal ends of the assembled form sections being open. 